Electronic devices use a resonator as a device for providing a time keeping function. As electronic devices become smaller, demand for smaller resonators increases. Accordingly, resonators manufactured using a micro electro mechanical systems (MEMS) technique attract attention.
In such a MEMS resonator, a retainer retains a vibrating portion, with a coupling portion interposed therebetween, such that the vibrating portion can vibrate. Conventionally, various measures have been taken in such a resonator to prevent vibration of the vibrating portion from being transmitted to the retainer as leakage vibration.
For example, Patent Document 1 (identified below) discloses a resonator using width-expansion vibration, in which a retaining arm connected to a node has a dynamic damper structure to suppress leakage of vibration to a retainer. Patent Document 2 (identified below) discloses a technique in which an auxiliary arm and a coupling portion are added between a contour resonator and a retainer to prevent leakage of vibration.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 7-7361.
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2008-166903.
In Patent Documents 1 and 2, undesired vibration from a vibrating portion is suppressed by a coupling portion, which has an auxiliary portion for absorbing vibration to prevent leakage of vibration from the vibrating portion to the retainer. However, this designs makes the shape of the coupling portion complex and increases the size of the coupling portion, and, therefore, it is difficult to reduce the size of the entire resonator. There is also a problem of reduced strength of the coupling portion.